Cutting efficiency of nickel-titanium rotary and reciprocating instruments after prolonged use.

The aim of the present study was to compare the cutting efficiency of Twisted File instruments used in continuous rotation or TF Adaptive motion and evaluate if prolonged use significantly affected their cutting ability. 20 new NiTi instruments were used in the present study (TF tip size 35, 0.06 taper; Sybron-Endo, Orange, CA, USA), divided into 2 subgroups of 10 instruments each, depending on which movement was selected on the endodontic motor. Group 1: TF instruments were activated using the program TF continuous rotation at 500 rpm and torque set at 2 N; Group 2: TF instruments were activated using the reciprocating TF Adaptive motion. Cutting efficiency was tested in a device developed to test the cutting ability of endodontic instruments. Each instrument cut 10 plastic blocks (10 uses) and the length of the surface cut in a plastic block after 1 min was measured in a computerized program with a precision of 0.1 mm. Maximum penetration depth was calculated after 1 use and after 10 uses, and mean and standard deviation (SD) of each group was calculated. Data were statistically analyzed with a one-way ANOVA test (P < 0.05). TF instruments used in continuous rotation (Group 1) cut a mean depth of 10.4 mm (SD = 0.6 mm) after the first use and 10.1 mm (SD 1.1 mm) after 10 uses, while TF instruments used with the Adaptive motion cut a mean depth of 9.9 mm (SD = 0.7 mm) after the first use and 9.6 mm (SD = 0.9 mm) after 10 uses. There was no statistically significant difference between the two groups investigated (P > 0.05) nor between instruments after 1 or 10 uses. In conclusion, the TFA motion showed a lateral cutting ability similar to continuous rotation and all tested instruments exhibited the same cutting ability after prolonged use.

Cyclic fatigue of instruments for endodontic glide path.

Endodontic glide path is the creation of a smooth patency from canal orifice to apex, which can be performed manually or with small tapered NiTi rotary instruments. The use of stainless steel (SS) hand K-files inserted in a reciprocating handpiece can be a possible alternative to create a mechanical glide path. The aim of this study was to compare the cyclic fatigue resistance between SS K-files used in a reciprocating motion and NiTi rotary instruments in artificial curved canals. Ten SS size 15 K-files used with the M4 handpiece (SybronEndo, Glendora, CA, USA) and ten PathFiles (Maillefer-Dentsply, Ballaigues, CH, Switzerland) NiTi rotary instruments size 16, 0.02 taper were tested for resistance to cyclic fatigue. The time to fracture inside an artificial curved canal was recorded for each instrument. Data were analyzed by one-way ANOVA and Tukey HSD test. Mean time (and SD) to failure was 464 s (±40.4) for the Group PF (NiTi rotary PathFile), and 1049 s (±24.8) for the Group M4 (SS K-files reciprocating) with a statistically significant difference between the two groups (p = 0.033). The SS 15 K-files used with the M4 handpiece showed a significant greater resistance to cyclic fatigue when compared to the NiTi rotary PathFiles. Therefore, the use of small size SS files in a reciprocating motion might be a rational choice for the creation of a mechanical endodontic glide path in curved root canals.

A new device to test cutting efficiency of mechanical endodontic instruments.

BACKGROUND: The purpose of the present study was to introduce a new device specifically designed to evaluate the cutting efficiency of mechanically driven endodontic instruments. MATERIAL AND METHODS: Twenty new Reciproc R25 (VDW, Munich, Germany) files were used to be investigated in the new device developed to test the cutting ability of endodontic instruments. The device consists of a main frame to which a mobile plastic support for the hand-piece is connected and a stainless-steel block containing a Plexiglas block against which the cutting efficiency of the instruments was tested. The length of the block cut in 1 minute was measured in a computerized program with a precision of 0.1mm. The instruments were activated by using a torque-controlled motor (Silver Reciproc; VDW, Munich, Germany) in a reciprocating movement by the "Reciproc ALL" program (Group 1) and in counter-clockwise rotation at 300 rpm (Group 2). Mean and standard deviations of each group were calculated and data were statistically analyzed with a one-way ANOVA test (P<0.05). RESULTS: Reciproc in reciprocation (Group 1) mean cut in the Plexiglas block was 8.6 mm (SD=0.6 mm), while Reciproc in rotation mean cut was 8.9 mm (SD=0.7 mm). There was no statistically significant difference between the 2 groups investigated (P>0.05). CONCLUSIONS: The cutting testing device evaluated in the present study was reliable and easy to use and may be effectively used to test cutting efficiency of both rotary and reciprocating mechanical endodontic instruments.

Fatigue resistance of rotary instruments manufactured using different nickel-titanium alloys: a comparative study.

The aim of this study was to investigate whether cyclic fatigue resistance is increased for Controlled Memory (CM) Nickel-Titanium (NiTi) instruments, compared to instruments produced using traditional NiTi and instruments produced using M-Wire alloy. Two groups of NiTi endodontic instruments consisting of identical instrument sizes (constant 0.06 taper and 0.25 tip diameter and constant 0.04 taper and 0.40 tip diameter) were tested: group A compared Hyflex™ CM, Vortex ™ and ProFile ™ size 25 and 0.06 taper and group B compared Hyflex™ CM, Vortex™ and ProFile™ size 40 and 0.04 taper. 10 files from each different subgroup were tested for cyclic fatigue resistance. Mean and standard deviations of the Number of Cycles to Failure (NCF) were calculated for each group and data were statistically analysed (p < 0.05). Hyflex™ CM instruments, size 25 and 0.06 taper, and size 40 and 0.04 taper, showed a significant increase in the mean number of cycles to failure when compared with size 25 and 0.06 taper Vortex™ and ProFile™. No statistically significant difference (p > 0.05) was noted between Vortex™ and ProFile™ in the tested sizes. The new manufacturing process involving memory shape heat treatment produced new NiTi rotary files (Hyflex™ CM) significantly more resistant to fatigue than instruments produced with other proprietary methods of treatment (Vortex™) and with the traditional NiTi grinding process (ProFile™).

Geometric analysis of maxillary first premolar prepared by two nickel-titanium rotary instruments.

AIM: The present study was conducted with the aim of evaluating and comparing the shaping ability of two Nickel-titanium rotary instruments, with two disparate design features, on root canal geometry of extracted human maxillary first premolars using microcomputed tomography. STUDY DESIGN: Twenty four bifurcated maxillary first premolars were divided into two groups and embedded in a rubber-based impression material. Both groups were submitted to micro-computed tomography before and after canal preparation (buccal and palatal) with either ProFile Vortex or Revo-S rotary instruments. Images were reconstructed and cross-sections corresponding to a distance 1, 2, 3, 4, 5, 6, and 7 mm from the anatomical apex were selected for canal transportation analysis. Volume changes were also measured. RESULTS: The degree and direction of canal transportation were non-significant for both instruments. Statistically significant differences were observed only between levels in the buccal canal in both groups. There was no significant difference between the two rotary systems in regards to the volume of dentin removed. CONCLUSION: Our findings showed that ProFile Vortex and Revo-S instruments respected the original root canal anatomy and behaved similarly. ProFile Vortex rotary systems produced with innovative process were concluded to shape the upper maxillary premolar by leading minimal canal transportation, similar to Revo-S, rotary systems produced from traditional process.

The influence of different angles and reciprocation on the shaping ability of two nickel-titanium rotary root canal instruments.

PURPOSE: The purpose of the present study was to investigate and compare the effect of different reciprocating movements and angles on the shaping ability of the WaveOne and the single-fle ProTaper F2 using cone beam computed tomography (CBCT). MATERIALS AND METHODS: The mesiobuccal canals of 40 extracted maxillary molars, with curvatures of 20 to 45° were coded and randomly divided into 4 equal experimental groups according to the instrument used (ProTaper F2 fle and Wa-veOne) and the reciprocation range, for both instruments, a 150° angle was used for cutting and a 30° angle was used for release. Group 1 - WaveOne primary 150° CCW rotation angle and 30° CW rotation angle; Group 2 - WaveOne 90° CCW rotation angle and 30° CW rotation angle; Group 3 - ProTaper F2 150° CW rotation angle and 30° CCW rotation angle; Group 4 - ProTaper F2 90° CW rotation angle and 30° CCW rotation angle. Canals were scanned before and after preparation using CBCT to evaluate the volumetric change, canal transportation and the canal centering ability at 2.6, 5.2 and 7.8 mm from the apex. The mean ± standard deviation (SD) values were analyzed, and the significance level was set at p ≤ 0.05. RESULTS: There was no significant difference in the amount of dentin removed among the experimental groups, except that WaveOne 150°CCW 30°CW significantly showed the least volume of dentin removed (0.40 ± 0.9) at 7.8 mm. All rotary systems tested in the different groups resulted in canal transportation in different directions at all examined levels. WaveOne 150°CCW 30°CW, demonstrated the lowest mean value of root canal transportation in both the mesial and furcal directions and in both the coronal and apical directions compared to the other groups. At the 7.8 level, WaveOne 150°CCW 30°CW yielded the highest mean centering ratio, whereas ProTaper F2 CW 150° CCW 30° yielded the lowest, statistically significant at p ≤ 0.05. CONCLUSION: The results of the present study demonstrated that differences among various reciprocating motions and angles could affect the shaping ability of a single-fle Nickel-titanium (NiTi) instrument.

Cyclic fatigue resistance of Mtwo NiTi rotary instruments used by experienced and novice operators--an in vivo and in vitro study.

BACKGROUND: The aim of the present study was to evaluate the cyclic fatigue resistance of Mtwo NiTi rotary instruments after clinical use by 1 experienced and 1 novice operator. MATERIAL/METHODS: Cyclic fatigue testing of instruments was performed on tapered artificial canals with a 5 mm radius of curvature and 60° angle of curvature. Twenty Mtwo instruments for each size were selected and divided into 2 groups: group A consisted of 10 instruments of each size used for shaping 10 root canals in molar teeth of patients by an experienced operator; group B consisted of 10 instruments of each size used for shaping 10 root canals in molar teeth of patients by a novice operator. Instruments were rotated until fracture occurred and the numbers of cycles to failure (NCF) were recorded. Data obtained were subjected to an independent sample t-test to determine statistical differences. The significance was determined at a 95% confidence level. RESULTS: No statistically significant difference (P<0.05) was noted between the instruments of groups A and B for all sizes. More instruments with visible signs of plastic deformation were identified for the novice operator. CONCLUSIONS: The clinical use of Mtwo NiTi rotary instruments by a novice operator did not significantly affect the cyclic fatigue resistance when compared with the control group of the same instrument sizes used by an experienced operator. It can be concluded that novice operators can use these instruments safely under the recommended technical guidelines.

Cyclic Fatigue Comparison of TruNatomy, Twisted File, and ProTaper Next Rotary Systems.

TruNatomy (TN; Dentsply Sirona, Maillefer, Ballaigues, Switzerland) is a newly released system that was not tested in any previous studies. The objective of this work is to evaluate cyclic fatigue resistance of the new file and compare it with the Twisted Files (TF) and ProTaper Next (PTN). Forty-five files were distributed into 3 groups: PTN X2 (size 25 and taper 0.06), TF (size 25 and taper 0.06), and TN prime file (size 26 and taper 0.04). Each group included 15 files. Lengths of all files were 25 mm. Cyclic fatigue testing was done using artificial stainless-steel canals with 60-degree curvature and 5 mm radius. Continuous rotation movement at 300 rpm was used until the file fractures. Time for file separation was recorded in seconds. The number of cycles to failure (NCF) mean and standard deviation for each group was calculated. For statistical analysis of data, ANOVA and Tukey's multiple comparison test were used. Mean and standard deviation (SD) of NCF were 259 ± 37.2, 521.67 ± 63.07 and 846.67 ± 37.16 for PTN, TF, and TN respectively. TN on average had significantly the highest NCF compared with PTN (p < 0.05) and TF (p < 0.05). TruNatomy file showed superior cyclic fatigue resistance. With its potential to preserve tooth structure, this file offers a good cyclic fatigue advantage. However, future studies are required to evaluate other properties of this file and to examine its clinical performance.

Detection of Bone Defects Using CBCT Exam in an Italian Population.

BACKGROUND: The aim of this study was to evaluate the in vivo incidence and the location of fenestrations in a young Italian population by using CBCT. MATERIALS AND METHODS: Fifty patients who had previously performed CBCT for planning third molar extraction or orthodontic therapy were selected for the study. No previous dental treatment had been performed on these patients. Overall, 1,395 teeth were evaluated. Root fenestrations were identified according to the definition of Davies and the American Association of Endodontists. Data was collected and statistically analyzed. RESULTS: Fenestrations were observed in 159 teeth out of 1,395 (11% of teeth). In the lower jaw, we found 68 fenestrations (5%) and 91 in the maxilla (6,5%). Incisors were the teeth with the highest incidence of fenestrations. CONCLUSION: The relative common finding (11%) of fenestration supports the need for CBCT exams before any surgical/implant treatment to avoid complications related to the initial presence of fenestrations. CBCT was found to be an effective and convenient tool for diagnosing fenestration.

A comparison of the canal centering ability of ProFile, K3, and RaCe Nickel Titanium rotary systems.

The purpose of this investigation was to compare the ability of three Nickel Titanium (NiTi) rotary systems (ProFile, K3, and RaCe) to centralize instrumentation relative to the original canal location and to determine the distance of transportation of these canals. Sixty mesial root canals mandibular molars with curvature ranging from 15 to 40 degrees were selected. The canals were divided randomly into three groups of 20 canals each. The roots were sectioned horizontally at 3 mm, 5 mm, and 8 mm from the root apex. Teeth were reassembled and instrumented according to the manufacturer's guidelines, with all groups being prepared to size 30 (0.06) taper master apical file. The cross-sections were digitally scanned before and after preparation, and image analysis software was used to assess the centering ability and the extent and direction of transportation. The three groups were statistically compared with analysis of variance and Tukey's HSD test. The results indicated that all three rotary NiTi systems used in this study were able to preserve dentin structure. The RaCe system significantly showed most transportation (p<0.05). The ProFile system was found to be the best for all variables measured in this study.

Fracture resistance of endodontically treated teeth restored with a bulkfill flowable material and a resin composite.

AIM: To determine and compare the fracture resistance of endodontically treated teeth restored with a bulk fill flowable material (SDR) and a traditional resin composite. METHODS: Thirty maxillary and 30 mandibular first molars were selected based on similar dimensions. After cleaning, shaping and filling of the root canals and adhesive procedures, specimens were assigned to 3 subgroups for each tooth type (n=10): Group A: control group, including intact teeth; Group B: access cavities were restored with a traditional resin composite (EsthetX; Dentsply-Italy, Rome, Italy); Group C: access cavities were restored with a bulk fill flowable composite (SDR; Dentsply-Italy), except 1.5 mm layer of the occlusal surface that was restored with the same resin composite as Group B. The specimens were subjected to compressive force in a material static-testing machine until fracture occurred, the maximum fracture load of the specimens was measured (N) and the type of fracture was recorded as favorable or unfavorable. Data were statistically analyzed with one-way analysis of variance (ANOVA) and Bonferroni tests (P<0.05). RESULTS: No statistically significant differences were found among groups (P<0.05). Fracture resistance of endodontically treated teeth restored with a traditional resin composite and with a bulk fill flowable composite (SDR) was similar in both maxillary and mandibular molars and showed no significant decrease in fracture resistance compared to intact specimens. CONCLUSIONS: No significant difference was observed in the mechanical fracture resistance of endodontically treated molars restored with traditional resin composite restorations compared to bulk fill flowable composite restorations.

In vitro evaluation of carrier based obturation technique: a CBCT study.

AIM: The goal of the study was to compare the ability of two different carrier based obturation (CBO) techniques to reach working length and fill in three-dimensions root canal systems, by using CBCT. MATERIALS AND METHODS: Twenty-six extracted molars were scanned with CBCT and 40 curved canals were selected (between 30° and 90°) and divided in two similar groups (n=20). All canals were prepared up to size 25 taper .06 using nickel-titanium instrumentation. The canals in the Group SC were obturated using Soft-Core obturators (Kerr, Romulus, Mi, USA), while Group TH canals (n= 20) were obturated using Thermafil Endodontic Obturators (Tulsa Dental Products, Tulsa, OK, USA), strictly following manufacturers' instructions for use. The obturations were analyzed by means of CBCT to measure the distance from the apical limit of obturation to the apical foramen and the presence of voids inside root canals. RESULTS: There was no significant difference between the two groups in the mean distance of the apical extent of the obturation (t test, p>0.05). Overfilling occurred in only 3 cases (2 in Group TH and 1 in Group SC). The percentages of voids in both groups were very low with no significant difference (Z test, p>0.05). CONCLUSIONS: The two tested CBO techniques showed similar positive results in terms of performance, even if, after checking with verifiers, in most cases the size of the selected Soft-Core obturator was one size smaller than Thermafil.

Deformations and cyclic fatigue resistance of nickel-titanium instruments inside a sequence.

AIM: To compare the effect of brushing motion on torsional and cyclic fatigue resistance of TF Adaptive instruments after clinical use. METHODS: 20 packs of TFA small sequence (SybronEndo, Orange, CA, USA) were used for this study and divided into two groups. Each instrument prepared one resin tooth, consisting in 4 canals with a complex anatomy. In group A, no brushing motion was performed. In group B, after the green instrument reached the working length, brushing motion with circumferential filing was performed for 15 seconds in each canal (overall 1 minute). All the instruments were then subjected to cyclic fatigue test and mean values and standard deviation for time to fracture were evaluated. Data were subjected to one-way analysis of variance and Bonferroni t-test procedure with a significance set at P < 0.05. RESULTS: No instruments were broken during preparation of root canals. Two TF Adaptive green and 5 yellow showed unwinding after intracanal clinical use. No statistically significant differences were found between green instruments of both groups (P > 0.05), while a statistically significant difference was found between the yellow instruments (P < 0.05), with group B showing an higher resistance to cyclic fatigue. CONCLUSIONS: A prolonged passive brushing motion did not adversely affected mechanical resistance of the instrument used for this purpose. Resistance to both deformations and cyclic fatigue of the second instrument within the TFA small sequence was enhanced by the coronal flaring provided by the brushing action of the first instrument used.

Professional attitudes and behaviors acquired during undergraduate education in the College of Dentistry, King Saud University.

OBJECTIVES: The purpose of the study was to investigate and evaluate the professional attitudes and behaviors acquired by students and recently graduated dentists during undergraduate education at King Saud University. METHODS: This cross-sectional survey used a 27-item questionnaire covering four cumulative theoretical dimensions of professionalism. Questionnaires were distributed to fifth-year students, interns, and demonstrators in the College of Dentistry during the academic year 2010-2011, and 203 completed questionnaires were used in analyses. Descriptive statistics were used to summarize responses. Crosstab and chi-squared tests were used, with statistical significance set at P < 0.05. RESULTS: The response rate was 79.3% (43.6% of males, 94% of females). Eighty-seven questionnaires were collected from fifth-year students, 92 from interns, and 24 from demonstrators. Many (59%) participants demonstrated high levels of professional attitudes and behaviors, whereas 40% did not comply with the elements of professionalism. Analyses revealed highly significant differences in certain responses with regard to gender, academic level, and grade point average. CONCLUSIONS: Although some participants did not possess all professional qualities, all participants possessed at least some elements of professionalism measured in this study. We thus recommend a strategic effort to develop targeted plans emphasizing professionalism at all levels of the dental school curriculum. High-profile role modeling, lectures, seminars, and academic ceremonies are ways of achieving professional development among dental students in parallel with their acquisition of basic scientific knowledge and clinical skills. This approach will formally and informally communicate that professionalism is a core value.

Microcomputed tomographic analysis of the furcation grooves of maxillary first premolars.

OBJECTIVES: The aims of this study were to conduct a morphometric analysis on the buccal furcation grooves in freshly extracted bifurcated maxillary first premolars (MFPs) and to correlate all anatomical measurements using microcomputed tomography. MATERIALS AND METHODS: Twenty-three human MFPs with bifurcated canals were selected for this study. The specimens were analyzed with microcomputed tomography. The length, the beginning, and the ending of the grooves were measured. The minimum cross-sectional canal wall thickness in the grooves was located, and the width of the dentin thickness was calculated. All measurements were recorded and statistically analyzed. RESULTS: The concavity of the grooves begins before the bifurcation site in 9/23 samples and after the bifurcation in 56.5% of samples. The groove length varied between 1.1-9 mm; the cross-sectional area with minimum palatal dentin thickness was 0.78±0.14 mm, which was located at a mean distance of 7.1 mm from the cementoenamel junction (CEJ) and 1.38 mm from the furcation. CONCLUSIONS: The presence of the furcation grooves in the palatal aspects of the buccal roots of the MFPs was 100%. The length, depth, location, and width of the dentin thickness of the grooves varied in relation to tooth length, bifurcation, and CEJ. These parameters should be taken into consideration before any endodontic or restorative procedures are performed. Reducing dentin width too vigorously by intracanal instrumentation can predispose to vertical root fractures or perforations; if a post cannot be avoided, it should not extend 6.5 mm from the CEJ.

The influence of three different instrumentation techniques on the incidence of postoperative pain after endodontic treatment.

AIMS: Apical extrusion of infected debris to the periradicular tissues is one of the principal causes of postoperative pain and discomfort. Recent researches have shown that reciprocating instrumentation techniques seem to significantly increase the amount of debris extruded beyond the apex and, consequently, the risk of postoperative pain. The goal of the present study was to evaluate and compare postoperative pain using three different nickel-titanium instrumentation techniques: a rotary crown-down technique using TF instruments (SybronEndo, Orange, Ca), a reciprocating single-file technique using WaveOne instruments (Maillefer DEntsply, Baillagues, CH), and a novel instrumentation technique (TF Adaptive, SybronEndo, Orange, Ca), using a unique, proprietary movement, combining reciprocation and continuous rotation. METHODS: Ninety patients requiring endodontic treatment on permanent premolar and molar teeth with non vital pulps preoperatively were included in the study. The patients were assigned into three groups of 30 patients each, trying to make the groups very similar, concerning the number of root canals, presence of initial pain and periapical lesions. The teeth in group 1 (n = 30) were instrumented with a crown-down technique using TF instruments, whilst those in group 2 (n = 30) were instrumented with a single-file technique using Waveone 08 25. The third group (n = 30) used the 3-file Tf Adaprtive sequence. All techniques were performed following manufacturers' instructions and all canals were shaped, cleaned and obturated in a single-visit by the same operator. The assessment of postoperative pain was carried out at 3 days by using a visual analogue scale. VAS pain scores were compared using one-way ANOVA post hoc Tukey test. A value of p < 0.05 was required for statistical significance. RESULTS: Results for VAS pain scores showed a statistically significant difference was found between the WaveOne (p=0,021) technique and the other two techniques. No statistical significant differences were found between TF and TF Adaptive (p= 0,087). When evaluating patient experiencing sever pain the incidence of symptoms was significantly higher with the WaveOne technique. CONCLUSIONS: Since the incidence of preoperative pain, the type of tooth and the pulp and periodontal pathology were quite similar between the three tested groups, and all the other variables (operator, irrigation, obturation) were identical, we may conclude that the difference in postoperative pain can be mainly related to the different instrumentation techniques.

Cyclic fatigue of nickel-titanium rotary instruments in a double (S-shaped) simulated curvature.

INTRODUCTION: The goal of the present study was to test the fatigue resistance of nickel-titanium rotary files in a double curvature (S-shaped) artificial root canal and to compare those results with single curvature artificial root canals. METHODS: Two nickel-titanium endodontic instruments consisting of identical instrument sizes (constant .06 taper and 0.25 tip diameter) were tested, ProFile instruments and Vortex instruments. Both instruments were tested for fatigue inside an artificial canal with a double curvature and inside a curved artificial canal with a single curvature. Ten instruments for each group were tested to fracture in continuous rotary motion at 300 rpm. Number of cycles to failure (NCF) was calculated to the nearest whole number, and the length of the fractured fragment was measured in millimeters. Data were statistically analyzed with a level of significance set at 95% confidence level. RESULTS: The NCF value was always statistically lower in the double curved artificial canal when compared with the single curve (P < .05) in both the apical and coronal curvatures. Statistically significant differences (P < .05) were noted between instruments of the same size of different brand only in the single curve; ProFile registered a mean of 633.5 ± 75.1 NCF, whereas Vortex registered a mean of 548 ± 48.9 NCF. CONCLUSIONS: Regardless of the differences between the instruments used in the present study, the results suggest that the more complex is the root canal, the more adverse are the effects on the cyclic fatigue resistance of the instruments.

Influence of different angles of reciprocation on the cyclic fatigue of nickel-titanium endodontic instruments.

INTRODUCTION: The purpose of this study was to evaluate cyclic fatigue fracture resistance of engine-driven nickel-titanium (K3XF) instruments under reciprocating movement in various angles. METHODS: Fifty K3XF size 40 taper 0.06 nickel-titanium instruments were divided randomly into 5 groups of 10 each. All instruments were subjected to cyclic fatigue tests. Instruments in groups 1-4 were tested by using different reciprocating motions, whereas instruments of group 5 (control group) were used in continuous rotation. All instruments were rotated or reciprocated until fracture occurred. Time to fracture was recorded, and data were statistically analyzed by using one-way analysis of variance, followed by Tukey honestly significant difference test for comparison between different groups. RESULTS: All reciprocating groups (groups 1-4) showed a significant increase in time to failure when compared with group 5 (continuous rotation) (P < .05). Mean time was significantly higher in group 1, followed by group 2. No significant difference was found between groups 3 and 4 (P = .251). Increasing the clockwise angle of reciprocation and consequently increasing the angle of progression for each reciprocation cycle reduced the resistance to cyclic fatigue. CONCLUSIONS: Movement kinematics (reciprocating movements in various angles) had a significant influence on the cyclic fatigue life of the tested nickel-titanium instruments.

Bending properties of a new nickel-titanium alloy with a lower percent by weight of nickel.

INTRODUCTION: The aim of the present study was to evaluate the bending properties of Hyflex instruments, which exhibit a lower percent in weight of nickel (52 Ni %wt) and compare them with other commercially available nickel-titanium (NiTi) rotary instruments. METHODS: Ten instruments with tip size 25, 0.06 taper of each of the following NiTi rotary instrumentation techniques were selected for the study: Hyflex, EndoSequence, ProFile, Hero, and Flexmasters. All instruments from each group were tested for stiffness by comparing their bending moment when they attained a 45-degree bend. Experimental procedures strictly followed testing methodology described in ISO 3630-1. All data were recorded and subjected to statistical evaluation by using analysis of variance test. Statistical significance was set at P < .05). RESULTS: Statistical analysis of the data revealed that Hyflex files were found to be the most flexible instruments, with a significant difference (P < .05) in comparison with the other instruments. Among the other files, a significant difference has been reported for EndoSequence instruments compared with ProFile, Hero, and FlexMaster (P < .05), whereas no significant differences have been reported among those 3 files (P > .05). CONCLUSIONS: Results of the present study have illustrated an increased flexibility of the new NiTi alloy over conventional NiTi alloy, and they highlight the potential of the new manufacturing process.

In vitro Evaluation of the Cytotoxicity of Different Root Canal Filling Materials.

OBJECTIVE: Aim of the present study was to evaluate the cytotoxicity of Real Seal 1 compared to other commercially available endodontic filling materials: Real Seal (SybronEndo, Orange, CA, USA) and Thermafil (Tulsa Dental, Tulsa, OK, USA). MATERIAL AND METHODS: Periodontal ligament cells from healthy patients were cultured. The eluate of Real Seal 1(TM) (RS1), Real Seal (RS) and Thermafil (TF) samples was used for the cells viability tests, both diluted (50%) or undiluted (100%). Incubation of the specimens was performed in culture medium for 24 h, 48 h and 72 h at 37 °C under sterile conditions. The cellular mortality was evaluated by MTT test. Results were statistically analysed and the statistical significance was set at p< 0.05. RESULTS: None of the studied materials showed toxic effects during the period of observation (0 -72 h) when compared to the control group. Only RS induced a very modest increase in cell mortality (about 3% at both concentrations used, during the first 24 hours), when increasing the incubation time, however, only the lower concentration continued to show modest toxicity. CONCLUSIONS: Results of the present study showed that all tested materials did not exhibit cytotoxic effects when compared to the control group.